DE2942180C2 - Process for the production of a heat insulating body - Google Patents

Abstract

In a process for making a thermal insulating body from highly insulating material, opacifier, reinforcing fiber mix and, if desired a binder, the materials are mixed together. The opacifier and/or the reinforcing fiber mix being mixed with a dispersant for forming a first-stage mix, which is then nextly mixed with the rest of the materials. The material is then compacted.

Description

a) 70-98% by weight of opacifier mixed with 30-2% by weight of dispersant and

b) the premix obtained is further mixed with the remaining materials.

2. The method according to claim 1, characterized in that that 10% by weight of dispersant is mixed with 90% by weight of opacifier.

3. The method according to claim 1 or 2, characterized in that the opacifier is organic or inorganic compounds are used.

4. The method according to any one of the preceding claims, characterized in that the grain size of the opacifier 0.2-20, preferably 1 - ΙΟμίη with a maximum of the frequency distribution between 2.5 and 5 μm.

5. The method according to any one of the preceding claims, characterized in that one is used as the opacifier Graphite, soot, inorganic oxides of titanium, llmenite rutile, chromium oxide, manganese oxide, iron oxide, Carbides of silicon, boron, tantalum or tungsten or their mixtures are used.

6. The method according to claim 5, characterized in that the opacifier is llmenit Fe-T1O3 used, which may be contaminated with manganese.

7. The method, in particular according to one of claims 1-6, for producing a heat insulating body from a highly dispersed insulation material, opacifier and a reinforcing fiber mixture, in which these materials are mixed and the resulting mixture to the heat insulating body is solidified, characterized in that one

a) adding up to 50% by weight of dispersant to the fiber mixture to be processed with mixing and

b) the premix obtained is further mixed with the remaining materials.

8. The method according to claim 7, characterized in that the fiber mixture to be processed 25-30% by weight of dispersant added.

9. The method according to any one of the preceding claims, characterized in that one is used as a reinforcing Fiber mixture Fibers made from asbestos, aluminum silicate, mineral fibers or organic fibers begins.

10. The method according to any one of the preceding claims, characterized in that the fiber diameter is in a range of 1-20, preferably 5-10 μm.

11. Method according to one of the preceding Claims, characterized in that the dispersants used are hydrophobicized inorganic substances or of an organic type. Pyrogenic silica or PTFE is used.

12. The method according to claim 11, characterized in that that hydrophobized silica is used as the dispersant

13. The method according to any one of the preceding claims, characterized in that the grain size of the dispersant is less than 1 µm.

The invention relates to a method for producing a heat insulating body according to the preamble of Claim 1.

From DE-AS 16 71 186 is a method for production a heat insulating material known in which a mixture based on airgel particles and inorganic fibers is deformed. This mixture consists of silicon dioxide - or silica - Airgel particles and ceramic aluminum silicate - or carbon fibers or mixtures thereof. To the Mixing these materials, they are placed in a container with a rotating vane in the bottom area After the container is closed, the material is swirled by turning the rotary vane and thus intimately mixed. The airgel and fiber material is in a preferred embodiment an opacifying material added before mixing. Then all the materials are dem Subjected mixing operation in the container containing a rotary vane.

The silica airgel particles generally have a particle diameter of less than 1 μm and have low density due to their large volume structure. As such a heat insulating material mostly consists of more than 50% of this airgel, almost the entire volume of the space is made of the heat insulating material produced body with the Aerogsl particles and the surrounding air is filled with the fibers and the opacifier in volume hardly matter.

Mixing tests have now shown that it is extremely difficult to produce one from more than 50% by weight of airgel particles to produce containing mixture, which also includes reinforcing fiber material and / or opacifiers contains. This is because relatively small amounts of opacifier and / or fibrous material turn into a large one The amount of airgel material added is often not uniform even after several hours of stirring To obtain mixture. This is because the rotary vane can only produce a thorough mixing in a limited area. In contrast, the amount of material located above the rotary vane only moves very slowly and hesitantly down to get mixed up there. Therefore, it often happens that when the rotation speed is high running rotary blades becomes hot due to the mixing, but on the other hand not a satisfactory one Can deliver mixing result. Such inhomogeneous mixing naturally suffers adversely affects the quality of the end product, its thermal conductivity and heat reflectivity will.

The same process of mixing all of the ingredients together is still out of the question DE-OS 27 54 956 and US-PS 30 55 831 known, so that the same difficulties are expected got to.

The invention is therefore based on the object of creating a method of the type mentioned at the beginning

which the mixing process can be carried out as energy-saving as possible without the heat-insulating Properties of the obtained product are deteriorated.

This object is achieved according to the characterizing features of claim 1

If opacifiers and / or the reinforcing fiber mixtures are mixed with the dispersant and brings the premix obtained with the filing isolating parts, which represent the major part of the final mixture together, so surprisingly one can find that the premix dissolves very easily in the isolating compound. This is probably the case due to the fact that the dispersant is the agglomerates, the opacifiers and / or the fibers have formed, dissolves and then keeps at a distance. These agglomerates are only very careful Treatment to dissolve, since those acting between the individual particles and forming the agglomerates Forces can be resolved by dispersing treatment and / or substances. By Separation of the individual opacifier particles or fiber components is further mixing with High-volume particles, which also tend to agglomerate, are made much easier, since these are high-volume Particles or agglomerates consisting of them between the individual, spaced apart opacifier particles and / or can push fiber components. It is of particular advantage if that The dispersant and the insulating material are identical, since the separation that has already taken place in the premix is a causes extremely easy dissolution of the opacifying agent and / or fiber material in the isolating agent mass, which ultimately amounts to a dilution of these materials.

As opacifiers that are added to increase the heat reflectivity, either organic or inorganic compounds that scatter, absorb or absorb the thermal radiation reflect, with the choice of substances on the use temperature must be taken into account. the The grain size of these opacifiers is usually in a range from 0.5 to 20 μm, preferably 1 to 10μπι, the maximum of the frequency distribution should be between 2.5 and 5 μm. About usable opacifiers include graphite and soot, provided the temperature is not too high, inorganic oxides of titanium, which may contain iron (III) oxide (ilmenite). Rutile, Chromium oxide, manganese oxide, iron oxide and carbides of silicon, boron, tantalum or tungsten or their Mixtures. Furthermore, metallic aluminum, tungsten or silicon, zirconium, titanium dioxide or Use lead monoxide and other substances that have a high heat reflection or IR refractive index. These opacifiers can be present in the heat insulating body in an amount of up to 60% by weight. The amount of opacifier used is selected according to the thermal radiation that occurs, with the The amount of opacifier used also increases with increasing temperature. The opacifier possesses also the advantage that there are large intermediate areas because of its large grain size compared to the insulating agent able to fill up, so that this reduces the thermal conductivity of the end product and thus the thermal quality is improved.

Ilmenit FeTiCh is particularly preferred as an opacifier, since this is very cheap and also easy to marry. This opacifier can be chemically bound with Manganese (Mn) may be contaminated.

All organic or inorganic fibers which improve the mechanical properties of the heat insulating body, in particular the surface adhesive properties, can be used as reinforcing fibers. Such fibers include mineral fibers, for example basalt fibers or glass fibers, asbestos fibers, aluminum silicate fibers, synthetic organic fibers based on polyamides, polyacrylic acid. Viscose. The fiber diameter should be in a range from 1 to 20, in particular 5 to 10 μm. The length d ^; These fibers are generally a few mm to a few cm. These reinforcing fibers can be added to the Geis mixture in an amount of up to 40% by weight.

Water-repellent substances can be used as dispersants inorganic or organic types are used, for example hydrophobized silica, pyrogenic Silicic acid or polymers, such as polytetrafluoroethylene, the silicas for reasons of cost are preferred.

This dispersant, the grain size of which is even less than 1 μm, is combined with the opacifier in one Weight ratio of 2:98 to 30:70, preferably 10:90, intimately mixed to form a premix. This premix is as long as one with the other components of the heat insulating body Blend the mixer until a uniform and extremely fine distribution of these ingredients is ensured. The dispersant serves as a spacer to the other components of the heat insulating body, see above that the individual binder particles are uniformly distributed in the insulating compound without agglomeration. Thus, the dispersant not only serves as a spacer to the individual insulating agent particles, but also as a mixing aid.

If the opacifier is still to be ground to the desired grain size, this can be done in the presence of the dispersant, as this effectively prevents agglomerate formation. It will intimately mixed with the dispersant before being incorporated into the insulating material and then thoroughly mixed ground to the desired grain size.

As a particulate insulating material, powder or fiber particles or mixtures thereof come into question. It can be agglomerates of finely divided Act particles with a grain size below 0.1 μm that have a tubular or porous structure. Such insulating materials include quartz or glass fibers, aluminum silicate fibers and other ceramic ones Fibers, powdered aluminum or mixtures of fly ash with expanded silica, finely divided Aluminum or chromium oxide and aerogels, for example of silica, chromium oxide, thorium oxide, Magnesium hydrate, aluminum oxide or mixtures thereof.

According to the invention, these aerogels can be used not only as insulating material, but also as dispersants can be used if they have an aggregate-splitting structure or are hydrophobized.

Such insulating materials also include fumed silica, which is produced from the chemical decomposition of silicon tetrachloride. The size of these particles is in the range of 1 mm - 2 mm. in particular special below 1 μm. In general, the heat insulating body consists of up to 95% of this insulating material, with preference! 30 to 85% insulation material is used.

In the method according to the invention for producing the heat insulating body, the premix is thereby produced that the opacifier and / or the reinforcing fiber with the dispersant in one usual mixer mixed. 2 to 30, in particular 10% by weight of dispersant and the corresponding amount are used Amount of opacifier. The ingredients of this mixture are added individually to the mixer. The mixture is then mixed until a uniform mixture is achieved. The mixing time is 1 « Depending on the material used, between 5 seconds and 5 minutes, especially in a period of 20-50 seconds. The premix produced in this way has a very fine, uniform distribution and has no agglomerates or larger fiber bodies more. This premix is added to the remaining isolating compound, this also being mixed for up to 5 minutes, preferably 20-50 seconds. The final mixture obtained can for example consist of approx. 60% fumed silica and 40% premix.

In a preferred embodiment, 10% pyrogenic silica, which is also used as an insulating material, and 90% opacifier, for example llmenite, is used.

This final mixture is pressed into sheets or molded parts in a press.

In the drawing, a device is shown, which schematically the entire mixing and filling station shows how to prepare a premix and a final mix. The mixing devices are shown in the drawing the process sequence carried out with it up to the filling station can be seen.

An opacifier 3 is added via a line 1 to a premixer 2, while a silica 4 via a feed hopper 12, which can feed lines Γ and 6 through a lock 13, is abandoned. The premix components arrive via lines 1 and Γ in the premixer, where they are then mixed and via a line 5 afterwards get into a main mixer 7 after mixing.

A reinforcing fiber 9 is via a line 6 'and a necessary for mixing the reinforcing fiber The amount of silica is also brought into the main mixer 7 via line 6, where the premix, the reinforcing fiber 9 and the silica are mixed.

Thereafter, the remaining silica is again fed to the main mixer 7 via line 6, where then the final mix is made. This final mixture is discharged into a silo 15 via a discharge line 14

■■ ΙΓ-.Ι, —1 - oil · 1 ΐ "Λ iC

uDcriuiirt. from where there is an ocnncckcniordersr ϊί? and a balance 17 arrives at a filling station 18.

Süirkungsfiber and the fumed silica accordingly supplied to the amount specified above for the fiber mixture.

The reinforcing fiber can, however, also be mixed with the fumed silica in a further premixer ground and added to the main mixer as a premix will.

It is still possible. Opacifier together with the reinforcing fiber in a premixer with the Mixing silica. However, it is always like that. that the proportions given above must be observed are when opacifiers and / or reinforcing fibers are to be dispersed.

After adding the remaining amount of silica, Ι-ΙαιίΓΐΙH / * ct * a tiH tf> iI H / »r t * A icr * Hi 1 ricr hr» t rif ft \ xnrr \ fjif *

Final mixing in main mixer 7 mixed for another 30-40 seconds. The final mixture obtained will be as above explained, further processed.

Trial report

Experimental facility

Wing mixer from Papenmeier with a capacity of 30 liters, which rotates at 1000 rev / min is operated;

Molding press for producing molded parts from a final mixture;

Thermal conductivity apparatus for determining the thermal conductivity according to DIN 52 612 on molded products.

Recipe The final mixture shows

59.6% Aerosil, which is suitable for both dispersion and

also serves for thermal insulation,
34.8% llmenit as opacifier and
5.6% AbOß fiber as reinforcement fiber

on.

Trial without premixing (state of the art)

Preparation of the premix and the final mix

55

To prepare the premix, the opacifier and the fumed silica are added in one, the order of addition being irrelevant. Then 30-40 SeL is mixed in the premixer if an opacifier is used and 3 to 5 minutes if mineral fiber wool is used to be mixed, and up to 50, preferably 25-30% by weight dispersant when reinforcing fiber is used. The premix obtained is transferred to the main mixer 7. After the premix has been poured in, the mixture is 596 g Aerosil, 348 g llmenit and 56 g A ^ O
are mixed for 40 seconds. The mixture obtained is pressed into a plate in the molding press.

The optical inspection of this plate shows that there are small bulges on the top and bottom which can be traced back to undissolved wool flakes. The cut surfaces are also included enriched with these wool flakes. As a result, this sheet does not have optimal mechanical properties.

The coefficient of thermal conductivity A (W / (m ■ k)) was also measured. This guide number is located at an average temperature of 250 ⁰ C at a value of 0.0262 for this disk.

Try with premix
(inventive method)

348 g llmenit and 56 g Al ₂ O ₃ are premixed with 100 g Aerosil for 10 seconds. The premix obtained is then mixed with 496 g of Aerosil for 30 seconds.

The mixture obtained is treated further in the same way as the above mixture.

Even the visual inspection of a molded part

dukts shows a completely homogeneous plate,
in which the fiber mixture becomes a strongly binding
Network has been converted.

The determination of the thermal conductivity showed
a value at 250 ⁰ C of 0.0277.

From this it can be seen that the plates produced by the method according to the invention, the
a thickness of about 8 inches and a bulk density
of about 333 kg / cm ^J , one by about 5%
have poorer thermal conductivity.

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Claims (1)

Patent claims: 1. A method for producing a heat insulating body from a highly dispersed insulating material, Opacifiers and a reinforcing fiber mixture in which these materials are intimately mixed, and the mixture obtained is solidified to form the heat insulating body, characterized in that that he